A method for fabricating an integrated circuit using a photo-lithographic process includes the steps of placing at least two anti-reflective coating layers between a reflective surface and another material. The indices of refraction, absorptions, and thicknesses of the at least two anti-reflective coating layers are chosen such that the amplitudes and phase differences of radiation reflected from the anti-reflective coating layers, as well as any other reflective surfaces below the anti-reflective coating layers, mutually cancel when combined. The invention may be practiced using more than two layers of anti-reflective coating. Multiple layers of anti-reflective coating may be used below an inter-level dielectric, in which case they may serve the additional purpose of functioning as an etch-stop.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A computer implemented method for designing anti-reflective coating layers with desirable properties comprising: a) modeling a first anti-reflective coating with a first index of refraction, a first absorption, and a first thickness, wherein the first thickness is slightly less than a total maximum allowable thickness for said anti-reflective coating layers based on the requirements of a desired integrated circuit fabrication process; b) modeling a second anti-reflective coating with a second index of refraction, a second absorption, and second thickness, wherein the first and second indices of refraction are different, and the combined thicknesses of the first and second anti-reflective coatings is approximately equal to said total maximum allowable thickness; c) modeling the reflective properties of the anti-reflective coatings using a lithography modeling program; d) evaluating the reflective properties of said first and second anti-reflective coatings relative to a set of desired reflective properties; e) adjusting the thicknesses, indices of refraction, and absorptions of the anti-reflective coatings based on said evaluating step; f) repeating steps c, d, and e to arrive at a solution for anti-reflective coating layers which provide desired reflective properties.
2. The method according to claim 1 , further comprising modeling one or more additional anti-reflective coating layers, modeling the reflective properties of said additional anti-reflective layers in the lithography modeling program during all reflective modeling steps c, evaluating the reflective properties of said additional anti-reflective layers during all evaluating steps d, and adjusting the thicknesses, indices of refraction, and absorptions of said additional anti-reflective layers during all adjusting steps c.
3. The method according to claim 1 , further comprising modeling one or more additional reflective layers and modeling the reflective properties of said additional reflective layers in the lithography modeling program during all reflective modeling steps c.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
March 14, 2003
June 17, 2008
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